To develop novel diagnostic and therapeutic techniques for neural crest tumors. 1. To characterize by peptide profile analysis, pathophysiologic abnormalities associated with peptide-secreting tumors. We will determine the association of the clinical abnormalities with constitutive and/or provoked peptides/substances to standard stimuli with and without somatostatin congener testing. 2. To develop and test in vivo pre- and intraoperative techniques to localize neural crest tumors, utilizing the somatostatin analogue, octreotide [TYR(3)] labeled with -123I for preoperative localization and -123I for intraoperative localization, cytoreduction, and tissue radioreceptor autoradiography.